The present invention relates to valves which have a service port to enable evaluation of fluid in a fluid system.
Back seating valves with service ports are known, and are used in a variety of applications, for example in refrigeration systems. The valve is located in a fluid system and includes first, second and third fluid passages. The first and second passages comprise the inlet and outlet passage for the valve, while the third passage comprises a service port. A valve element can be moved between open, intermediate and closed positions in the valve to i) allow fluid to pass from the inlet passage to the outlet passage in the valve substantially uninterrupted during normal system operation (open position); ii) open a flow path to the service port for evacuation, charging, reclaiming and pressure-tapping the system (intermediate position); or iii) completely close the flow path between the first and second passages during shipping and maintenance (closed position). The valve element is typically externally accessible to allow manual manipulation of the valve into the respective positions, although the valve could also be operated automatically using electromechanical devices (e.g., solenoids, etc.).
It is believed that many of the commercially-available back seating valves include a valve element and a valve seat which are separately assembled into the valve body, sometimes from opposite ends of the body. The valve seat may be first inserted through the service port opening and welded, brazed or threaded into the valve body, and the valve element is then inserted through the inlet passage or outlet passage opening before the inlet passage tube/fitting or outlet passage tube/fitting is attached to the valve body. The brazing/welding/threading of the valve seat, however, adds a potential leak path through the system; while the brazing/welding process requires more expensive valve seats to be used that can withstand the higher temperatures associated with the brazing/welding process.
It is also believed that many of the available valves include numerous components which can require complicated and/or time-consuming assembly steps, and which thereby add to the manufacturing, assembly and maintenance/repair costs of the valve, and increase the potential leak paths through the valve. This can all contribute to a higher operating cost for the fluid system. The additional component parts can also increase the over-all size and weight of the valve.
Some of the back seating valves also allow an operator to remove the valve element while the valve is connected within the fluid system. While the field-repair of a valve may be appropriate in some circumstances, it can also lead to accidental removal of a valve element while the fluid system is operating, thereby allowing fluid to spill from the valve or the valve to be disabled; and can allow incompatible or inappropriate replacement valve elements to be used with the back-seating valve.
It is thereby believed there is a demand for an improved back-seating valve with service port which i) has fewer brazing and/or welding steps and fewer components to reduce manufacturing and assembly costs, and to reduce leak paths; and ii) prevents disassembly of the valve in the field.
The present invention provides a novel and unique back seating valve with a service port. The back seating valve of the present invention has few braze/welding joints and few components, which reduces manufacturing and assembly costs and reduces leak paths; and the valve cannot be disassembled in the field.
According to the present invention, the back seating valve includes a valve plug having a central threaded through-bore; and a valve element with an elongated stem and an integral valve head. The stem has a threaded portion which is screwed into the through-bore in the valve plug. The valve plug and valve stem are initially preassembled, and then inserted into the valve body. The valve body is then mechanically formed (e.g., crimped, coined or magnetically formed) to retain the valve plug in the valve body without the use of welding or brazing. The valve plug has an external, non-cylindrical geometry, which, after the valve body is crimped and adopts the non-cylindrical geometry of the valve plug, prevents the valve plug from rotating within the valve body. The valve body also has an internal shoulder which supports one end of the valve plug, and is mechanically narrowed at its opposite open end to support the other end of the valve plug, thereby also preventing axial movement of the valve plug in the valve body.
The valve plug has a first valve seat (back valve seat) at its upstream end, and the valve element can be rotated to bring the valve head into sealing engagement with the first valve seat. An enlarged counterbore extends inwardly into the valve plug from the valve seat, and a plurality of radial passages fluidly interconnect the counterbore with an annular channel outwardly surrounding the valve plug. The channel is in axial alignment with a service port in the valve body to provide a flow path through the valve plug. A second valve seat (front valve seat), for the inlet passage, is also provided axially opposite from the back valve seat for the valve plug.
The stem of the valve element has a portion which extends externally from the downstream end of the valve plug, and is externally accessible to rotate the valve element, and bring the valve head into and out of sealing engagement with the valve seats.
The valve element can be moved into an open position for normal system operation where the valve head is in sealing engagement with the back valve seat and fluid can flow substantially uninterrupted (without significant pressure drop) from the inlet passage to the outlet passage. The valve element can also be moved into a closed position, where the valve head is in sealing engagement with the front valve seat, to prevent fluid flow through the valve during maintenance and shipping. The valve element can also be moved into an intermediate position, where the valve head is spaced from both the front and back valve seats, such that a flow path is opened to the service passage for evacuating, charging, reclaiming and pressure-tapping the system. A stem cap fits over the end of the valve body to enclose the external portion of the stem when the valve element is not being moved.
The valve plug and valve element can be formed of inexpensive material, such as elastomers and plastics, as the plug is not subject to brazing or welding temperatures during assembly. This can also reduce the weight of the valve. The valve element and valve plug can also be pre-tested prior to being inserted into the valve body, to ensure the valve is in compliance with operating specifications. The pre-assembled valve plug and valve element can be easily inserted into the valve body from one end of the body, and after the valve body is mechanically deformed, cannot be removed from the valve body.
Appropriate seals can be provided between the valve stem and the valve plug and/or between the valve plug and the valve body to prevent fluid leaking from the valve.
Thus, it should be appreciated that the back seating valve of the present invention has few braze/welding joints and few components, which reduces manufacturing and assembly costs, and reduces leak paths; and cannot be disassembled in the field.
Further features of the present invention will become apparent to those skilled in the art upon reviewing the following specification and attached drawings.